98 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



but I have made cell 4 larger in the diagram. It is of course only 

 in very regular colonies that the averages of the single right and 

 left pairs of angles and sides will give a figure approximating the 

 typical surface tension configuration. 



SiXTEEN-CELLED COLONY OF PeDIASTRUM BoRYANUM 



Interior angles and sides of cells 

 Central cell i. 



In colony. In diagram. 



Angles: 



igi^ = 



Sides: 



iglji = 113.5° + 'V^'" = 102.5° = 216° H- 2 



^ig-2^3 = 81° + i^i' = 93-5° = 174-5° - 2 = 



i = 9.5 mm. + i^ = 10.5 mm. = 20 

 -ji = 9.25 mm. -\- r* = 8.75 mm. = iJ 



2 = 



Cells 2-6. 

 Angles: 



kgif^ = 121° + ki^i = 128° = 249° ^ 2 = 



ig^k' = 125° + k'gH' = 121° + i'g'k' = 129° + 



i^g'k' = 129° = 504° -^ 4 = 



^ig2^2 = 136° + iJ'o^k^ = 132° = 268° -^ 2 = 



i3g2^2 = i_^2° + i'g'k' = 134° = 276° ^ 2 = 



o^ek = 115° + oek = 108.5° + o'e'k' = 109.5° + 

 o-e^k' = 106° + oh'k' = 119° + oV^^ = 109° 

 = 667° ^ 6 = 



JfeVo» = 1^0° + y^Vo« = 95° = 215° -=- 2 = 



k-e'-o* = 108° + )feW = 116° = 224° -^ 2 = 112°^ 



III" 



108° 

 87.2° 



10 mm. 

 9 mm. 



124-5 



126° 



134° 

 138° 



iir 



107' 

 120"^ 



Sides: 



odp = 109° + o'd'p' = 113° + oH~p'- = 102° + 

 o7j7p7 = 970 _[_ o8f/8^8 = 107° 4- oM^p^ = 109° + 



oH^p^ = 100° + o^d'^p^' = 112° = 849° -^ 8 106° 



oV^^'i = 104° 4- ohl'^p^ = 114° = 218 -^ 2 = 109* 100° 



ife = 8 mm. 4- ^^ = 9 mm. 4- k'- = 6.5 mm. + 

 k^ = 8.5 mm. + ^' = 8 mm. = 40.0 -^ 5 = 8 mm. 



= 7.5 mm. 4- 0^ = 6 mm. -\- 0- = 6.5 mm. 4- 

 0' = 7 mm. 4- 0'^ = 7 nim. 4- 0' = 4 mm. 4- 

 0^ = 8 mm. 4- 0" = 7 mm. 4- 0^ = 7 mm. 4- 

 o^ = 6 mm. = 66 -^ 10 = 6.6 mm. 



